The present disclosure relates to dark polycarbonate compositions that have a combination of low temperature impact resistance, thin wall flame retardance (FR), good electrical tracking resistance, and reduced halogen content. These polycarbonate compositions can be useful for various insulating applications.
Polycarbonates (PC) are synthetic engineering thermoplastic resins, and are a useful class of polymers having many beneficial properties. With their strength and clarity, polycarbonate resins offer many significant advantages and are used for a number of different commercial applications, including electronic engineering (E&E) parts, mechanical parts and so on.
Because of their broad use, it is desirable to provide polycarbonates having good flame retardance. The market is also moving towards articles having thin walls for purposes of slimness, weight reduction, and size reduction of the overall final product. With decreasing wall thickness, it becomes increasingly difficult to render the article flame retardant.
Desirably, polycarbonate compositions should also have good flow properties. Good flow properties reflect how easily the polymeric composition can be poured into a mold for forming the shape of the part. Better impact properties are also desirable. A conventional way of increasing impact resistance is by increasing the weight average molecular weight of the polymer, but this typically also reduces the flow properties and makes it difficult to fill complex or thin-walled molds.
There remains a need in the art for flame retardant polycarbonate compositions that have a dark color, provide good electrical tracking resistance, and maintain ductility at low temperatures. In this regard, polycarbonates exhibiting good flame retardance, low temperature impact strength, and flame retardance performance have been developed. However, these polycarbonates also require brominated fire retardant additives and are only available in light colors due to the presence of high TiO2 content (for impact strength and tracking resistance). Prior attempts to create dark colored polycarbonates with thin wall flame retardant properties, non-brominated FR additives, and low temperature impact strength were unsuccessful, as the presence of higher levels of carbon black and/or lower levels of TiO2 led to a loss in low temperature impact and electrical tracking resistance.